Some self-healing epoxy materials contain microcapsules with healing agent formulations that, upon damage, are released and may react to heal the damage site in an epoxy material. However, most reagents capable of curing epoxy resins at ambient conditions are amines and amides with amphiphilic properties. Thus, common encapsulation approaches based on the formation of stable oil-in-water emulsions cannot be employed, as the amine or amide functionality remains at the interface between the oil and water phases, thereby disrupting the encapsulation process.
For these reasons, self-healing chemistries designed and tested for epoxies have largely been based on alternative chemistries such as ring opening metathesis polymerization (ROMP), silanol condensation, and hydrosilylation. The difficulty of encapsulating amines also has led to the development of other approaches to employ amine-functionalized curing agents without compartmentalization via typical microencapsulation processes, such as the use of latent reactivity in an epoxy matrix. Other approaches include the production of hollow capsules or the use of other porous carriers, such as glass particles, followed by infiltration of an amine curing agent into these capsules or porous carriers. These approaches have shown limited success.